1. Field of the Invention
The present invention relates to papermaker's fabrics for supporting and conveying a paper web through the papermaking process. More particularly, the present invention relates to a papermaker's fabric formed from a plurality of tessellated elements.
2. Description of the Prior Art
In the papermaking process, a papermaker's fabric is used in the form of an endless belt-like structure which is supported by and advanced through the equipment by various machine rolls. This process and the various sections of the papermaking equipment, formation, press and dryer, will be known to those skilled in the art.
Recent developments in the field of papermaker's fabrics have lead to widespread use of synthetic materials in the fabrics. Previously, most fabrics were made through the use of a weaving process, using either the endless or flat technique. More recently, spiral fabrics have come into use. Spiral fabrics are not woven in the traditional sense but are produced by forming a plurality of spiral coils on a mandrel and then interconnecting the spiral coils through the use of joining wires or pintles. In spiral fabrics, the spiral coils may be generally equated with machine direction yarns and the pintles may be generally equated with cross machine direction yarns.
Although all of the prior art fabrics have found applications and have generally performed satisfactorily, it has been determined that each technique has its drawbacks. With respect to endless fabrics, it is essential to know the final finished width and length of the fabric before the weaving process starts. Accordingly, each fabric is custom made to a particular application. With respect to flat woven fabrics, it is possible to produce continuous lengths of fabric which may be cut to size, however, it is generally required that the width of the fabric be determined at the time of weaving. With respect to spiral mesh fabrics, they provide tremendous flexibility as to assembly of fabrics in different lengths and widths but are less adaptable to desired changes in drainage, permeability and surface characteristics.
Prior art fabrics have almost always been limited to materials which are available in fiber form or to materials which could be formed into fibers. The fabric designer almost always had to make compromises when designing the fabric because of the limited materials available. For example, when designing for either stretch resistance or wear resistance, the designer frequently had to compromise the fineness of the fabric. Although these compromises were acceptable in many applications, the required compromises frequently resulted in either less than ideal fabrics or less than ideal product.
Although all of the prior art fabrics have performed satisfactorily in given applications, the art still desires a means for quickly and economically producing fabrics of various lengths, widths and surface characteristics. In all papermaking fabrics, the parameters of air permeability, drainage, moisture retention and fabric stability are of concern to the fabric producer and user.
In view of the above, it is the intent of the present invention to produce papermakers fabrics inexpensively and efficiently without any reduction in fabric reliability or adaptability. It is a further intent of the present invention to eliminate design compromises, improve uniformity of the fabric and to eliminate the reliance on a limited range of materials.
In order to achieve such a fabric, one assembles a plurality of elements to achieve the necessary length and width of the fabric. It is contemplated that elements will be provided in standard sizes. However, as will be recognized by those skilled in the art, the required length of fabric will vary according to papermaking equipment. Accordingly, it is contemplated that the elements will be provided in standard sizes which will constitute the majority of the fabric and will be provided in certain other standard complementary sizes in order to form the final closure and the end or selvage of the fabric width.
Consider, for example, the need to finally close a fabric into an endless structure. In order to provide the final closure, the elements may be provided with a width which is the same as the remaining element but with a shorter dimension between the leading and trailing edges. These complementary elements may be provided in a variety of lengths less than the standard elements. Likewise, the end or selvage elements may be provided with the standard length between leading and trailing edges but with a somewhat reduced width. Once again, these elements may be provided in various widths. After final assembly of the tessellation, the width and/or selvage ends may be further trimmed by known techniques which are common with respect to cutting synthetic materials. In this matter, a reasonably precise fabric with uniform selvages may be inexpensively and efficiently assembled.